Typical computer systems, especially computer systems using graphical user interfaces (GUIs), are optimized for accepting user input from one or more discrete input devices, such as a keyboard for entering text, and a pointing device, such as a mouse with one or more buttons, for operating the user interface. An example of such a GUI is the user interface for the WINDOWS® computer operating system (available from Microsoft Corporation of Redmond, Wash.). The ubiquitous keyboard and mouse interface provides for fast creation and modification of documents, spreadsheets, database fields, drawings, photos, webpages, and the like.
Recently, however, pen-based computing systems, such as tablet PCs, personal digital assistants, and the like, have been increasing in popularity. In pen-based computing systems, user input advantageously may be introduced using an electronic “pen” or stylus (e.g., akin to writing with a pen or pencil on a piece of paper). Indeed, in at least some pen-based computing systems, all user input is capable of being entered and manipulated using an electronic pen input device, and the user interface is fully controllable using only the electronic pen.
As pen based computing systems become more popular, users are increasingly entering more data in the form of electronic ink. As with any computer input device, errors are possible and corrections must be made. The ability to erase electronic ink from the user interface is necessary and the ability to use the electronic pen to erase this ink can be highly efficient.